Mechanical and Civil Engineering Seminar

Abstract: The development of advanced materials with desired mechanical properties requires a fundamental understanding of the physics of deformation and failure behavior of materials over a wide range of length and time scales. Measurement of strength at high dynamic pressures is critical for applications such as space shielding, hypersonic vehicles, armor protection, and planetary science. However, the experimental techniques to investigate the strength of materials at high pressures are limited. This talk will present the recent advances in the pressure shear plate impact (PSPI) technique to study the material behavior at high dynamic pressures involving shock waves. The high-pressure PSPI experiments provide a unique methodology for extracting the complete stress-strain behavior of materials at pressures approaching 50 GPa. The results from experiments on oxygen-free high conductivity (OFHC) copper and pure magnesium will be discussed. A strong pressure hardening in strength is observed in copper when pressure increases from 10 to 43 GPa and cannot be explained using existing models. The experimental results reveal the scaling of shear modulus and strength are quite different, which were previously assumed to be the same. The atomistic mechanisms responsible for pressure-dependent strength are explored using molecular dynamics simulations. In magnesium, softened strength response at high pressures is observed due to shock-induced crystal rotation and temperature rise.

Bio: Dr. Suraj Ravindran is currently a postdoctoral scholar at the Graduate Aerospace Laboratories, California Institute of Technology (GALCIT), working on the high-pressure dynamic behavior of materials. He received his Ph.D. in mechanical engineering from the University of South Carolina in 2018. His research interests are in the mechanics of materials under extreme conditions of pressure, strain rate, and temperature.